Fluid pressure brake control apparatus



F. S. WHALEY FLUID PRESSURE BRAKE CONTROL APPARATUS Filed Dec. 28, 1949 w v $0 F U HO June 23, 1953 "USE IN VEN TOR. .Fred 8. whaleg BY ATTORNEY Patented June 23, 1953 FLUID PRESSURE BRAKE CONTROL APPARATUS Fred S. Whaley, Greensburg,

Westinghouse Air Brak tion of Pennsylvania Pa., assignor to e Company, a corpora- Application December 28, 1949, Serial No. 135,419

Claims.

ly in section, of a fluid pressure brake control apparatus embodying the invention associated with a draw works cable drum; Fig. 2 is a schematic representation in cross-section of a relay valve device, a plurality of which are employed in the apparatus shown in Fig. 1; and Fig. 3 is a schematic representation in cross-section of a self-lapping valve device, several of which are employed in the control apparatus shown in Fig. 1.

Description As shown in the drawing, numeral I indicates a rotary element such as a cable drum on which may be wound hoisting cable (not shown) such as is employed on rotary oil well rigs for supporting drill pipe etc. Through turning of the drum in one direction or the other, the cable will Wind or unwind on the drum for raising and lowering drill pipe, tools etc. in and out of the hole being drilled.

To control the rate of turning movement of the drum I and thereby control the rate of unwinding of the cable wound thereon, for example, fluid pressure brakes 4a and 4b are provided at opposite ends of the drum. The brakes 4a and 41) comprise cylindrical shaped elements 40 and 401 which are attached to the drum I at its opposite ends, respectively. The brakes 4a, and 41) further comprise fluid pressure brake cylinder devices 2 and 3 operable to effect move ment of friction shoes 5 into frictional engage-- ment with cylindrical elements 40 and 4d, respectively, thereby to effect a braking oi the drum I. v

The brake cylinder devices 2 and 3 are alike, and schematically each may comprise a casing containin a brake cylinder piston 6 slidably disposed therein which is subject opposingly to pressure of fluid in a brake cylinder pressure chamber l at one side and to force of the usual piston return spring 8 disposed in a spring chamthe degree of brake application.

derrick and ina bet 9 at its opposite side. The spring chamber 9 is constantly open to atmosphere by way of a port I I). The piston 6 is operatively connected to the respective brake shoe 5 by means of a piston rod II attached to the piston for reciprocable movement therewith. In each of the brake cylinder devices 2 and 3; in response to supply of fluid under pressure to the pressure chamber 1, the piston 6 will oppose action of the return spring 8 and move in the direction of the chamber 9 for engaging the brake shoe 5 with the member 40 or 4d. The shoe 5 will exert a force against the member 40, 4d according to the degree of pressure in the pressure chamber 1. The force exerted by the shoe 5 against the member 40, 4d determines the degree of restraint imposed to oppose rotation of the drum I, which degree of restraint will hereinafter be referred to as The degree of brake application may be increased or decreased by regulation of the pressure of fluid in the chamber I; Upon substantial complete release of fluid under pressure from the brake cylinder pressure chamber 1, the return spring 8 will move the piston 6 back to a rest position, in which it is shown in the drawing, carrying the respective brake shoe 5 to a retracted position out of engagement with the member 40 or 4d, which action will hereinafter be referred to as release of the brake application by the respective brake cylinder device.

The apparatus for controlling operation of the brake cylinder devices 2 and 3 is enclosed in the drawing by a dash line to indicate that such apparatus may be encasedin such as a roving control stand which may be located some distance away from the brake cylinder devices 2 and 3, at the hoisting cable drum I, to allow an operator, such as a driller on a rotary oil drilling rig, to select a point of vantage from which he may coordinate operation of the cable drum with operations being performed by a crew of men located at different stations, such as on the floor of a derrickmans perch situated a considerable distance above the derrick floor.

For effecting variations in pressure of fluid in the pressure chambers I in the brake cylinder devices 2 and 3, self-lapping valve devices I2 and I3, respectively, are provided. Referring to Fig. 3, each of the self-lapping valve devices I2 and I 3 may comprise a casing 12 having a fluid pressure supply chamber I3, a delivery chamber 14, and an exhaust chamber I5 therein. A supply valve seat element I6, attached to an operating stem 16' is adapted for reciprocable movement 84 of element 82.

within the casing 12. Element 16 is open intermediate its ends to the supply chamber 13 which is connected by way of ports H to a central cavity 18 provided within said element, and at its lower end, as viewed in the drawing, said element is open to the delivery chamber H which is connected to cavity 18 by way of a supply valve seat 19. A supply valve 88 in the form of a ball may be disposed within cavity I8 for controlling communication between the supply chamber 13 and the delivery chamber 14. A bias spring8l is disposed in the cavity 18 arranged to urge the valve 80 toward a normally closed position on seat 19. An exhaust valve seat element 82, secured for reciprocable movement with deflection 'of a diaphragm 83, is open at one end to the delivery chamber 14 and has an exhaustvalve seat 84 formed therein. Valve seatelement 82 extends through the diaphragm 83 with its opposite end disposed in the exhaust chamber 15 and has a central opening 85 extending from end-to end and through the valve seat 84 at the one end. An exhaust valve 85, connected to the supply valve 88 by a pin 88', and also in the form of a ball, is disposed in delivery chamber 14 to cooperate with the seat 84 in element 82 for controlling communication via openin 85 between said delivery chamber and the exhaust chamber I5. A bias spring 88, disposed in the delivery chamber 14, is interposed between seat elements 16, 82 for biasing the seat element 16 in the direction of chamber 13. The diaphragm 83 is subject on one sideto pressure of fluid in a diaphragm chamber 81, which pressure of fluid is that of the delivery chamber 14, the two chambers being connected one with the other by way of ports 88. The opposite side of the diaphragm 83 is exposed to atmosphere by way of a port 89 in the casing. A compression control spring 80 is disposed in the exhaust chamber 15, interposed between the diaphragm and-an adjustable spring seat element SI, for determining the degree of deflection of said diaphragm for any given pressure condition in the delivery chamber 14. The adjustable spring seat 8| is provided to allow for changing precompression of the control spring 88.

When stem 16 is moved inwardly of the easing 12 a certain distance, the attached seat element 18 is moved downwardly, as viewed in the I drawing, while the supply valve seat 19 formed in the end of element 16 is moved away from the supply valve 88. At this time, supply valve 80 will remain stationary due to seating engagement of the attached exhaust valve 85 on seat When the supply valve seat 19 moves away from the supply valve 88, supply chamber 13 is opened to delivery chamber 14 by way of ports 11, cavity 18 and seat 19. Fluid under pressure from a source of supply which may be connected to supply chamber 13 will then flow into the delivery chamber 14 where the pressure of fluid will thus be caused to increase. Pressure of fluid in diaphragm chambe 8'! open to chamber 14, being greater than the atmospheric pressure in chamber 15, will deflect diaphragm 83 against action of spring 90 in the direction of the last mentioned chamber. Deflection of diaphragm 83 will carry the exhaust valve seat element 82 with it. Bias spring 8| will cause the supply valve 88 and exhaust valve 85' to follow movement of element 82, while said exhaust valve remains seated on seat- 84 in the end of said element, until'said supply valve seats on seat 19 in element 16. Upon seating of the supply valve 80, the supply chamber 13 is closed to the delivery chamber 14 and further increase in pressure in the latter chamber thereby will be prevented. In absence of further increase in delivery pressure in the diaphragm chamber 81, the pressure force on one side of diaphragm 83 will balance with the spring force on its opposite side and further deflection of said diaphragm will cease. The supply valve 88 and the exhaust valve 85' will remain seated. If, at this time, stem 15 were moved inwardly a greater amount, element 16 would again be moved downwardly to unseat from the supply valve 80, and the above described action would repeat, and a corresponding'increase in pressure of fluid would be secured in the delivery chamber 14. The pressure of fluid thus obtained in the delivery chamber 14 will vary in substantial proportion to the degree of inward movement of the operating stem 16. The minimum pressure which will be held in the delivery chamber 14 will depend on the degree of precompression of the control spring 90, which precompression may be changed by adjustment of the spring seat element 8|.

If, subsequently, the operating stem 18' is allowed to be moved outwardly of casing '12 by action of spring 86 to a more extended position, the supply valve and attached exhaust valve will be carried with it. The exhaust valve 85 is thus unseated from seat 84 in element 82, and the delivery chamber 14 is thereby opened by way of opening 85 in said element to the exhaust chamber 15. Delivery pressure in chamber I4 is thus caused to reduce, and such reduction, re-

flected in the diaphragm chamber 81, allows the contro1 spring to deflect the diaphragm 83 upwardly. Upward deflection of the diaphragm 83 carries the element 82 into engagement with the exhaust valve 85'. The delivery chamber 14 is thus closed off from the exhaust chamber 15 and. further reduction in delivery pressure thereby will be prevented. Under such condition, the diaphragm 83 ceases further deflection, and both the supply valve 80 and the exhaust valve 85' remain seated. A reduced delivery pressure, de-

termined by position of the operating stem 16',

is thus secured.

Summarizing action of the self-lapping valve devices l2 and I3 it will be seen that with the proper adjustment of the spring 90, and with fluid at adequate pressure in chamber 13, the pressure of fluid in the delivery chamber 14 is determined by position of element 18 as adjusted through positioning of stem 16. By effecting displacement of stem 16 inwardly of the casing 12, pressure of fluid in delivery chamber 14 will be increased in amount proportional to the degree of said displacement. Conversely, as outward movement of stem 18' is effected, the pressure of fluid in the delivery chamber 14 will be decreased in amount proportional to degree of said outward movement. In both valve devices l2 and I3 a certain outermost limit position of the stems I6 is defined byrest positions of a respective cam 93. The outermost limit position of stem 18' in devices 12 and I3 corresponds to a certain minimum pressure of fluid in delivery chamber 14. vMaximum inward displacement of stem 18' calls for maximum delivery pressure. Still further, both the valve device l2, and the valve device 13 are self-maintaining, that is, any

tendency for increase or decrease in pressure of sated for to prevent such occurrence in manner as aforedescribed.

The two earns 99 are identical and are secured for turning movement one with the other by a shaft El l to which is attached an operators handie 95 which provides for turning the shaft and cams for simultaneous equal adjustment in the position of the respective stems iii to cause simultaneous equal regulation in pressure of fluid in the respective chambers it and thereby in pressure chambers l of the brake cylinder devices 2, 3 to which the chambers are connected by pipes ifll and W2, respectively. Ihe cams 93 are so shaped that as the handle 95 is rocked in a counter-clockwise direction, as viewed in the drawing, the stems 19' will be displaced inwardly distances proportional to the degree of rocking movement of said handle. Conversely, as the handle 95 is rocked in the opposite direction the stems l will be allowed to move outwardly of the devices I2 and it in amount proportional to the degree of rocking movement of the handle.

The supply chambers 13 in the self-lapping valve devices I2 and I3 are connected to pipes 98 and 99, respectively, which when connected to a fluid pressure supply pipe I act to convey fluid under pressure, say one hundred pounds for example, to the respective supply chambers I3, so that devices 52 and i3 may be operated to eifect operation and control of the brake cylinder devices 2 and 3 through the medium of the brake cylinder pipes ItI and :er connected, respectively, to the brake cylinder pressure chambers l in the brake cylinder devices 2 and 3.

With the pipes 99 and 99 both charged with fluid at a certain pressure, such as one hundred pounds for chosen example, when the operators handle 95 is moved from the position in which it is shown in the drawing and titled Full Release to a position indicated in the drawing by a dot-and-dash line titled Intermediate, the pressure of fluid in the brake cylinder pipes Iili and Hi2 and connected brake cylinder pressure 7 simultaneously will be increased from substantially atmospheric pressure to some pressure such as fifty pounds. A detent (not shown) may be provided to locate such Intermediate position. When the handle 95 is moved between the Intermediate position and a position titled Full Application, the pressure of fluid in the brake cylinder pipes [0i and I02 and connected brake cylinder pressure chambers i will be varied simultaneously between fifty and one-hundred pounds, respectively, for example.

For reasons which hereinafter will become obvious, relay valve devices ltd and I84 are provided which control communicaton between the 9&3, 99, respectively, and the supply pipe iilil.

Referring to Fig. 2, the relay valve devices and I0 3 may each comprise a casing II3 having a diaphragm li t disposed therein and subject to pressure of fluid in a diaphragm chamber M5 on one side and to pressure of fluid in a chamber lid on its opposite side, which latter chamber is open to the exterior of the casing via a port IIl. Also formed in the easing are chambers H9, H9 and I 20 chamber II8 being separated from chamber I It by a partition iii and from chamber H9 by a partition I22. A partition E23 separates chambers H9, 20. A valve I24 is disposed in chamber I20 for controlling communication between said chamber and the chamber I I 9. Valve I25 may be secured to a fluted stem I30 slidably mounted in a suitvalve I29.

diaphragm chamber I I5, 4&4 will respond to close able bore extending through the partition I 29, a seat beingformed in one end of said bore to accommodate said valve. A bias spring I20 is disposed in chamber I20, arranged to urge the valve I24 in the direction of its seat. A valve I29, similar to valve I24, is disposed in chamber IIB for controlling communication between said chamber and the chamber II9. For slidably guiding valve I29, a fluted stem I25 is provided which is slidably disposed in a suitable bore openingthrough partition I22. A valve seat is formed in partition I22 for accommodating the Stems I25, I project into and meet in the chamber I I9 in such a manner that action of bias spring I 28 on valve I24, in urging same in the direction of its seat, at the same time,

through said stems, urges valve I29 in a direction away from its respective seat. Ir" valve I29 is seated, valve I24, consequently, will be unseated. Valve I29 is operably connected to the diaphragm I I 4 by means of a rod or stem I33 extending therebetween through a bore in partition I2I in which said rod is slidably disposed. A control spring I36 is provided in chamber I I6, arranged to oppose deflection of the diaphragm I I4 in the direction of chamber I I8 as caused by pressure of fluid in chamber H5 for determining the degree of said pressure necessary for effecting operation of valves I24, I29.

In operation, when their respective chambers are vented to atmosphere the relay valve devices I03 and I04 will respond to a certain. pressure of fluid in the diaphragm chamber I I5 to close valve I29 and open valve I24 to connect the chamber II9 to chamber I20. quent certain reduction in Upon a subsepressure of fluid in relay valve devices I03, their valve I24 and to open their valve I29 to connect chamber H8 to chamber I I9.

In the relay valve device I 03; its chamber I20 is connected-to a pipe I40 which may either be open to the atmosphere or may be blanked off as will hereinafter become apparent from subsequent description; its chamber H9 is connected to the pipe 98; and its chamber H8 is connected to the supply pipe I09 by way of a pipe I4I, a volume chamber I42, a pipe Hi3, and

a choke I44 and check valve I45 arranged in parallel relationship.

In the relay valve device I04; the chamber I I9 is connected to the supply pipe I00 by way of a pipe I47, a volume chamber I43, a pipe I49, and

.a choke I and check valve I 5| arranged in parallel relationship; its chamber I I9 is connected to the pipe 99; and its chamber I20 is connected to a pipe I52 which may either be open to the atmosphere or may be blanked, that is, closed.

In both of the relay valve devices I93 and I04, the chamber H6 at one side of the diaphragm H4 isopen to atmosphere via port II'I.

For controlling operation of the relay valve devices I03 and I04, relay valve devices I59 and IEI are provided, respectively, aswell as a push button type of valve device I62.

The relay valve devices I60 and Iiii may be substantially alike the relay valve devices I 03 and I04 previously described, and as shown in Fig. 2.

In the relay valve device I69; its chamber I20 is connected to the corresponding chamber I 2i! in the relay valve device IGI by way of a pipe relay valve device I03 by way or a-pipe- 181.;lts chamber I I8 is connected to atmosphere by way of pipe 168; its chamber H6 is connected, via its port H1, to the pipe 98; and its control chamber H5 is connected to a branch of the pipe 99.

In the relay valve device I6I; its chamber H9 is connected to the control chamber H5 in the relay valve device I04 by way of a pipe I69; its chamber H8 is connectedto atmosphere by way of a pipe I10; its chamber H6 is connected to a branch of the pipe 99, and its control chamber H5 is connected to a branch of the pipe 98.

In the relay valve devices I03, I04, I60 and. IGI, when their respective valves I24 are seated and their respective valves I29 'unscated, the communication between the chambers H9 and H8 which is established by way of the'unseated valve I29 in each valve devicenhereinafterwill be referred to as communication I80, indicated symbolically in. Fig. 1 by solid lines bearing the reference numeral I80; similarly, a dash line bearing reference numeral I8I in Fig. 1 will hereinafter represent the communication I8! which is established in each of the relay valve devices I03, I04, I60, I6I between chamber H9 and chamber I20 which is established when the valve I29 is seated and the valve I24 is unseated.

The relay valve devices I60 and I6I will operate similarly to the relay valve devices I03 and I04 with the exception that when their respective chambers H6 are charged with fluid under pressure, the efiect of fluid under pressure in their respective control chambers H5 is nullified so that their respective communications I80 remain established until their respective chambers I I6 are vented to atmosphere The push button valve device I62, schematrcally, may comprise a casing 200 having an exhaust chamber MI and an inlet chamber 202 formed therein, The exhaust chamber 20I is constantly open to atmosphere by Way of a port 203 in the casing, while the inlet chamber 202 is connected to a branch of the pipe I55. A valve 204 controls a communication between the inlet and exhaust chambers 20I, 202. The valve 204 when in a closed position in which it is shown in the drawing, closes the chamber 282'from the chamber 20I, and when in an open position, opens the chamber 202 to the chamber 20I, hence to the atmosphere. A compression spring 205 disposed in the chamber 202 is arranged to bias the valve 204 to its closed position. A push button 206 is attached by means of a stem 201 to the valve 204 for actuating same to its open position by manual operation. Upon release of force exerted manually on the push button 206, the spring 205 will return the valve 204 to its closed position.

To furnish fluid under pressure for the system supply pipe I90 a compressor 300 is provided which may be driven through a belt'by a motor (not shown) to supply fluid under pressure to a reservoir 30I with which the pipe I has a connection.

Pressure gauges 400, 40I, 402 and 403 are connected to pipes IOI, I02, 98 and 99, respectively, to indicate the pressure of fluid in these pipes to an operator.

Operation Assume that the reservoir 30I is charged with fluid under pressure, that the pipes 98 and 99 are charged with fluid under pressure and that therefore both chambers H6 and H in both relay valve devices I60 and I6I are charged with fluid under pressure from the pipes 98 and 99 so that the respective communication I .in each .of these relay valve devices will be established,

as will be appreciated from previous description. With the respective communication I80 established in each of the relay valve devices I60 and iGI, the respective control chamber H5 in each of the relay valve devices I03 and I04 will be vented to atmosphere by way of pipes I61, I68 and I69, I10, respectively. With their respective control chambers I I5 thus vented, the relay valve devices I03 and I04 will each have their respective communication I80 established, connecting pipes 98 and 99 to pipes MI and I41, respectively, thence to the system supply pipe I00 by way of volume chambers I42, I48, pipes I43, I49, and check valves I45, I5I or chokes I44, I50. The pipe I65 will be charged with fluid under pressure from the pipe I00 by way of choke I66. The push button 206 of valve device I62 will be fully extended so that its chamber 202 connected to pipe I65 will be closed to its chamber 2ll which is open to atmosphere. Assume that the operators handle 95 is in its Full Release position, with the respective stems 16' of the valve devices 62 and I3 fully extended so that the brake cylinder pipes WI and I02 both will be vented with the brakes 4a and 4b fully released as will be appreciated from previous description.

Assume now that the operator desires to apply the brakes 4a and 41). He will move the operators handle 95 out of its Full Release position toward or to its Intermediate position to effect simultaneous supply of fluid from pipes 98 and 99 to the brake cylinder pressure chambers 1 by way of pipes I0! and I02 to cause engagement of brake shoes 5 with elements 40 and 4d, applying a braking force in restraint of turning movement of the drum I according to the degree of pressure thus applied to the brake cylinder pressure chambers 1.

According to a feature of the invention, should a break or severe leak occur in one of the brake cylinder pipes IOI, I02, brake cylinder pipe IIlI, for example, while the brakes 4a and 4b are applied, fluid under pressure in the pressure chamber 1 in brake cylinder device 2 will escape through the break in the brake cylinder pipe, releasing the brake 4a, while fluid under pressure also will escape suddenly from the chamber 14 in the valve device I2 by way of the break in pipe IOI. With the brake cylinder pipe I 02 intact, the brake 4b will remain applied. In the valve device I2, when fluid under pressure escapes from the chamber 14, pressure in the chamber 81 will become reduced suddenly as fluid leaves through ports 88 and the chamber 14. In response to sudden venting of the chamber 81, the diaphragm 93 will respond to move seat element 82 in the direction of chamber 14, carrymg the seated exhaust valve with it and thereby causing unseating of the supply valve 80, whereupon fluid under pressure from the pipe 98 will flow rapidly by way of the chamber 13, ports 11, chamber 18, and the unseated supply valve in an effort to make up for the loss of fluid in the chamber 14 which escaped by way of the broken pipe IOI Such sudden flow of fluid under pressure from the pipe 98 will tend to reduce the pressure of fluid in the pipe I00 by way of the communication I80 in relay valve device I03, pipe I4I, chamber I42, pipe I43 and check valve I45. The volume chamber I42 will store suflicient fluid under pressure however to supply the surge of fluid under pressure to the valve device I2, thereby reducing the tendency for the pressure in the pipe I to be reduced by such surge. The choke I50 and check valve II act to prevent any sudden reduction in pressure in pipe I06 from reducin the pressure of fluid in the brake cylinder device 3 by way of the pipe I02, device I3, pipe 09, device I04, pipe I41, chamber I48 and pipe I49. Since the pipe 99 remains charged with fluid under pressure and is not influenced by a break in the pipe IOI, the control chamber H5 in the relay valve device I60 will remain charged while the pressure in the chamber II6 reduces substantially with the surge of fluid under pressure flowing from pipe 98 to the break in pipe WI. The relay valve device I 50 with its control chamber II5 charged will therefore respond to such reduction in its chamber II6 to disestablish its communication I60 and to establish its communication I8I, thereby disconnecting the pipe Iii! from atmosphere via pipe I68 and connecting said pipe I61 to the pipe I65, whereupon fluid under pressure will flow from the supply pipe I00, via the choke I66, pipe I85, said communication NH, and said pipe I6! to the control chamber I15 in the relay valve device I058. The relay valve device I03 Will then respond to disestablish its communication I80 and to establish its communication I8I, thereby dis-.

connecting the pipe 96 from the pipe I4I, hence from the supply pipe I00 to prevent further loss or" fluid under pressure from the system by Way of the valve device I2 and the break in the pipe itl as assumed. The communication I8I in the relay valve device I 03 connects the pipe 96 to the pipe I46 which may be either vented or plugged, since the essential function of the device its is to disestablish connection between the broken pipe I0! and the supply pipe I00 in the event that a break occurs.

With the pipe 98, hence the ruptured brake cylinder pipe IGI, thus isolated from the supply ipe I00, the source of fluid under pressure remains intact so that fluid at full reservoir pressure exists in the pipe 99, available for supply to the pressure chamber 1 in the brake cylinder devicefi. The operators handle 95 may be moved beyond Intermediate position toward Full Application position to increase the pressure of fluid in the pressure chamber I in the brake cyl inder device 3 to effect increased application of the brake 3 to compensate for the loss in braking of the drum I when the brake 4a is rendered ineffective by loss of pressure in the brake cylinder pipe 'I0-I assumed to have been ruptured. The volume chamber I48 will act as an immediate source of fluid under pressure for supply to the brake cylinder device 3 so that such may be accomplished efiectively and readily.

Upon repair of the ruptured brake cylinder pipe Iili, communication between the pipe 98 and the supply pipe I00 may be reestablished to reinstate the idle brake 4a by manually depressing the push button 206 of the valve device I62. Upon depression of the push button 206 of valve device I62, the valve 204 in device I62 will be unseated to vent the pipe I65, thereby allowing for release of fluid under pressure from the control chamber H5 in the relay valve device I03 by way of the pipe I6'I, the communication ISI in the relay valve device I60 and said pipe I65. The choke I66 prevents excessive release of fluid under pressure from the supply pipe I00 when the pipe I65 is vented via the device I62. Upon release of fluid under pressure from its control chamber II5, the relay valve device I03 will rehe repaired brake cylinder pipe NH.

spond to reestablish its communication I which again connects the pipe 98 to the pipe MI and therefore to the supply pipe I00 by way of the volume chamber I42, the pipe I43, the choke EM and check valve I45. The pipe 98 will again become pressurized with fluid at full reservoir pressure from the pipe I00 which condition will be indicated by the pressure gauge 802, the chamber H6 in the relay valve device I60 will become pressurized with fluid from the pipe 98 and respond to disconnect pipe I61 from the pipe I65 and to connect said pipe I6! to pipe I68 to atmosphere, whereupon the operator may release the push button 208 to allow the valve 204 in the valve device E62 to close, thereby preventing further release of fluid under pressure from the pipe H80 via choke I66 and pipe I 65. With the operators handle in a position between Intermediate and Full Application position as assumed,- when the pipe 98 is again connected to the pipe I00, fluid under pressure from the pipe 98 will flow by way of the unseated supply valve 80 in the valvedevice I2 to the pressure chamber 7 in the brake cylinder device 2 by way of The gauge 400 in pipe IOI will indicate to the operator whether or not the pressure of fluid thus supplied to the device 2 is maintained and therefore whether or not the repair has been successful. I

To reduce the degree of or to release the'application of both brakes 4a and 4b, simultaneously, the operators handle 95 may be moved back toward or to Full Release position to reduce the pressure of fluid in the respective chambers "i in brake cylinder devices 2 and 3, as will be appreciated from previous description. Application and release of both brakes 4a and 4b will again be effected in unison through adjustment in position of the operators lever 95 to and between the Full Release and Intermediate positions.

It will be appreciated that should the brake cylinder pipe I02 rupture or develop a severe leak, in fashion-similar to that aforedescribed in connection with pipe- I 0!, the apparatus will function to disestablish communication between the pipe99, thereby the ruptured brake cylinder pipe I02, and the supply pipe I00by operation of the relay valve device I84 to prevent loss of working fluid from the system while maintaining the brake ta applicable or applied while the brake 4b is rendered ineffective by the rupture in brake cylinder pipe I02.

Summary It will now be seen that I have provided fluid pressure control apparatus for controlling operation of a pair of brake cylinders for braking such as a hoisting drum. The control apparatus may be adjusted manually to effect regulation of pressure of fluid from a source thereof to and its release from the brake cylinder devices by way of respective brake cylinder pipes which opera= tively connect the control apparatus with such brake cylinder devices. During normal operation of the brake cylinders in unison, the pressure may be varied therein below a certain limit value to obtain adequate braking of the drum. In event that one or the other of the brake cylinder. devices should be rendered ineffective by development of an excessive leak in a respective brake cylinder pipe, through rupture or the like, the control apparatus will respond automatically to isolate the ruptured brake cylinder 

